Direct access arrangement (DAA) circuitry is often utilized to connect electrical systems to telephone networks such as the POTS network. Thus, the DAA circuitry provides the necessary circuitry that enables communication between an electrical system and the standard two wire phone line.
As shown in FIG. 1, DAA circuitry 100 is utilized provide a communication channel from the TIP and RING phone lines 110 and a host system 114. The host system 114 may be any of a wide range of electrical systems, and may be for example, a personal computer, a laptop computer, a set-top box, or other electrical devices. The DAA circuitry 100 may include an isolation barrier 106. The isolation barrier 106 provides the electrical isolation required by various governmental standards for isolation between the telephone line network and electrically powered circuitry. Example isolation barriers may include for example, capacitors, transformers, opto-couplers and/or any other devices that provide the required isolation. The DAA circuitry may also include system side circuitry 102 and line side circuitry 104. The system side circuitry may include integrated circuits and/or discrete devices that are located on the system side of the isolation barrier 106. The line side circuitry may include integrated circuits and/or discrete devices that are located on the telephone line side of the isolation barrier 106. Exemplary prior art DAA circuitry is shown in U.S. Pat. Nos. 6,385,235 and 6,304, 597, the disclosures of which are each incorporated herein by reference.
The system side circuitry 102 may communicate with the host system 114 through a communication interface 116. The communication interface 116 may provide data and control information between the host system 114 and the DAA circuitry 100. In one exemplary application, the host system may include dedicated modem hardware. Such modem hardware provides the necessary modem data processing to communicate data from a host system across a phone line. In another exemplary application the host system may include a “soft” modem. A soft modem is implemented by utilizing system hardware resources (such the CPU of a personal computer) in conjunction with modem software that runs on the host system in order to provide the necessary modem functionality. In another exemplary application, the modem functionality may be performed within the system side circuitry 102.
No matter what type of modem is implemented, the DAA circuitry generally must be configured in a manner such that it is compatible with the communication interface standard utilized by the host system 114. Exemplary communication interface standards that the communication interface 116 may be in compliance with include for the Peripheral Component Interconnect (PCI) standard, the AC-97 standard, the Azalia standard, and others interfaces. The PCI standard is a common I/O bus standard that is well known in the art that provides a shared data path between processors and peripheral controllers. To provide a standard interface for computer system audio applications, Intel Corporation has sponsored the Audio Code '97 (AC-97) Component Specification. Note that, as used here, AC-97 operational specifications include the current AC-97 operational specifications and any revisions or updates to those specifications, as well as any follow-on specifications that incorporate features of the current AC-97 operational specifications. The Audio CODEC '97 Component Specification, revision 2.1 (May 22, 1998) is hereby incorporated by reference in its entirety. The AC-97 specifications enable a controller residing in a computer system to communicate with a variety of devices, including telecommunication devices through a TDM interface such as a five wire TDM interface. Some of those telecommunication devices, for example, data modems, may use telephone lines to communicate with other devices and exchange data. The Azalia standard is an upgrade of the AC-97 also sponsored by Intel Corporation. The Azalia standard provides a five wire interface as with the AC-97 standard, however, the Azalia interface is based upon a packet based protocol rather than a TDM based protocol. The Azalia Specification revision 0.7 is hereby incorporated by reference in its entirety. In prior art DAA solutions, the DAA circuitry is typically configured with a dedicated interface that operates with only one interface standard. For example, the Silicon Laboratories Si3038 product is a DAA that has an interface that complies with the AC-97 specification (the datasheet for the Si3038 is expressly incorporated herein by reference).
FIG. 1A provides a block diagram of an exemplary DAA configured to operate with the AC-97 interface standard. As shown in FIG. 1A, a system side integrated circuit 102A may include clock circuitry 122, AC-97 digital interface circuitry 118, and control interface 124. An isolation interface 126 may also be provided. The line side integrated circuit 104A may include an isolation interface 128, hybrid and dc termination circuitry 130 and control signal circuitry 132 (such as ring detect circuitry, off-hook detect circuitry, etc.). A plurality of lines 134 may couple the line side integrated circuit 104A to discrete components that are used to couple the line side integrated circuit to the TIP and RING phone lines of a phone line network. An isolation barrier 106 may be provided between the line side integrated circuit 104A and the system side integrated circuit 102A. The isolation barrier 106 provides the electrical isolation of the phone line network as required by various U.S. and foreign governmental and international bodies and/or standards, such as for example as required by the FCC.
To accommodate an interface standard, the DAA circuitry 100 is generally hardwired or hard programmed to operate with a single known interface standard. It would be desirable to implement a DAA that may operate with a plurality of interface standards.